1. Field of the Invention
The present invention relates to a land-mounted flap gate that is installed in a wide-span opening such as the top surface of the embankment of a seawall or the like as a countermeasure against, for example, high tides or tidal waves.
2. Description of Related Art
An example of a flap gate is a floating body-type flap gate that is installed in an opening of a seawall and that raises door bodies using the buoyancy of incoming water to block the opening in order to prevent water increased at the time of water increase from flowing into living spaces or underground spaces (see, e.g., Japanese Unexamined Patent Application Publication No. 2012-241449).
When such a floating body-type flap gate is installed on the top surface of the embankment of a seawall, a required height is achieved only in case of emergency and the height of the embankment can be kept low in a normal situation, so that a view can be unobstructed from a land side to a sea side, and thus the landscape is not spoiled by the flap gate.
However, in the case of this floating body-type flap gate that is installed on the top surface of the embankment of a seawall, the length of a part for blocking the inflow of sea water becomes longer when compared with the floating body-type flap gate that is installed in the opening of a seawall, so that the number of door bodies connected with each other increases and the number of connections between the door bodies also increases. Furthermore, it is difficult to generate sufficient auxiliary force to the operation of raising or lowering door bodies with only both sides of the floating body-type flap gate.
As illustrated in FIG. 8, this connection between neighboring door bodies is performed by bonding flanges 2 along the whole side surfaces of neighboring door bodies 1 by means of welding, superimposing a waterproof rubber 3 and a pressing plate 4 on the upper surface of each of the flanges 2, and inserting a waterproof film 5 which connects the door bodies 1 in a watertight manner between the waterproof rubber 3 and pressing plate 4 of these neighboring door bodies 1, and then fastening bolts 6 and nuts 7 at predetermined intervals.
However, the floating body-type flap gate regularly requires a floating inspection on the start of raising and an operation inspection from a lowered state to a raised state and from a raised state to a lowered state, as well as a visual appearance inspection.
When the floating inspection on the start of raising or the operation inspection between the lowered state and the raised state is performed, it is difficult to inspect all door bodies at one time because the floating body-type flap gate that is installed on the top surface of the embankment of a seawall has a large number of door bodies connected to each other.
In particular, the floating inspection on the start of raising is performed after all the connections between neighboring door bodies have been released in order not to influence other neighboring door bodies. In this case, it is very cumbersome to unfasten a plurality of bolts and nuts that secure waterproof films that connect the neighboring door bodies to each other in a watertight manner.